Rubber compounds may be vulcanized within a mold to form a molded article. For example, a rubber tire can be formed by pressing a tire blank into mold surfaces and heating under pressure to vulcanize the rubber and to form tire features (e.g., treads) defined by corresponding mold surface features. The molded tire is released from the mold surfaces in a de-molding step. In some cases, the molded tire may stick to the mold surfaces which can increase de-molding times and can lead to uneven de-molding which can damage the molded tire. The sticking may be the result of the relatively complex shape of certain tire mold surfaces. Also, contamination (e.g., sulfur, zinc salts, oils and waxes) which is deposited on mold surfaces during the vulcanization, can enhance sticking. Such contamination may also damage mold surfaces which can lead to formation of defects on surfaces of the molded tires.
Molds may be periodically cleaned or reconditioned to remove contamination, for example, using a bead blasting techniques. However, such techniques may damage mold surfaces by creating pits or other defects. In some cases, molds may only be reconditioned a limited number of times prior to being unsuitable for use.
Other solutions have been proposed to reduce mold sticking and/or to mitigate the build up of contamination on mold surfaces. For example, one technique has involved spraying a solvent-based silicon release agent on mold surfaces. However, this can form a caramelized surface on the mold over time which may contribute to build up of contamination and loss of surface finish. Other techniques have formed coatings (e.g., polymeric material coatings) on mold surfaces. A conventional approach for forming such coatings has been to utilize spray and dip techniques. However, such techniques may not be able to form conformal coatings of relatively constant thickness on mold surface features having small widths and/or high aspect ratios. Instead, coatings formed using such techniques may lead to coating thickness variations across certain mold features and/or may not conformally coat the entire mold surface that defines certain features as shown schematically in FIG. 1. This impairs the ability to form small features on molded tires with desired accuracy using molds coated with such techniques. Furthermore, such techniques can lead to blockage of vent holes in the mold that are important to ensure proper release of vapors during vulcanization. Consequently, such techniques may require that vent holes be manually opened after the coating process.